Process for making insulated concrete tilt-up walls and resultant product

ABSTRACT

In a method of making insulated concrete tilt-up panels, an insulating material such as polystyrene is formed into a desired shape corresponding to the panel shape. Attachment grooves are formed across the surface of the insulating material. Preferably, the attachment grooves have a substantially triangular cross-section. The insulating material is laid groove-side-up in a concrete form and wet concrete is poured into the form. The concrete fills the grooves, attaching the insulation to the concrete panel. When the concrete is cured, the panel may be stood up and set in place so that the insulating material forms the exterior surface of the panel. A finishing material may be applied to the exterior surface of the panel. A panel set for use in constructing low-income residential housing includes four concrete tilt-up panels. The insulating material and concrete forms may be prepared in the quantity desired for the entire construction project and transported to a casting area at the construction site. The panels may be rapidly cast and assembled, reducing the time and labor required to complete the project.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of co-pending provisionalapplication No. 60/937,027 filed Jun. 25, 2007.

FIELD OF INVENTION

This invention relates to concrete wall construction. This inventionrelates particularly to a process for creating insulated concretetilt-up wall panels and the resultant products.

BACKGROUND

Building structures using tilt-up concrete wall panels are well known inthe art. They can significantly reduce the initial cost of construction,increase the life of the structure and reduce maintenance cost. Tilt-uppanels are made under controlled conditions and the exterior surface canbe inexpensively finished with rollers to shape an attractive product.Such panels can be pre-cast, fabricated and stored in the factory andthen transported to the building site, or made in-situ, forming thepanels at the building site. Walls, and therefore buildings, can beassembled rapidly using the panels.

In general, tilt-up concrete panels are made by attaching a concreteform having the dimensions of the desired panel to a casting surface,then filling the cavity of the concrete form with freshly mixed concreteand letting the concrete cure. Concrete forms are conventionallyconstructed on-site as needed for each building and made of wood ormetal; these forms are removed after the panel is cured. Alternatively,the forms may be pre-made forms of foam, plastic or metal into which theconcrete is poured; these forms become integral with the panel. Metalties such as rebar span the forming panels to connect and maintain thepositions of the opposed forming panels as the concrete is placed. Oftenthe ties are formed into grids, webs, chairs, or a combination thereof.The ties are left in the concrete as it hardens, and thus reinforce thestrength of the panels, as well as provide support for connecting theformed panels to each other when constructing a continuous wall. Theedges of the tilt-up panels may be beveled to provide some tolerancewhen placing the panels together in the wall, and the joints createdbetween the tilt-up panels are caulked.

Concrete walls have large thermal mass, but are poor insulators. Thatis, once the heat or cold is absorbed by the concrete, it is conductedunfortunately rather well. It would therefore be advantageous toinsulate a concrete tilt-up panel. Further, it would be moreadvantageous to insulate the tilt-up panel along its exterior surface,so that the thermal mass of the concrete is cooled or heated by theenvironment inside the structure rather than from the outside. A wallusing such panels would reduce energy consumption of heating and airconditioning units by regulating the temperature of the interior space.

Some known methods of insulating tilt-up panel walls use insulatingmaterials commonly known in the construction industry, such as rigidpre-formed foam panels or spray foam that hardens. However, it isdifficult to attach rigid foam panels to the relatively smooth finishedexterior surface of a concrete tilt-up wall, and spray foam does notstick in place long enough to harden. A common solution is to insert alayer of insulation between two layers of concrete, either duringformation of a single panel or once the panels are in place in the wall.This solution does not take full advantage of the thermal mass of thetilt-up wall, allowing part of the wall to heat or cool withoutinsulation while providing a smaller thermal mass for regulation of theinterior temperature. Further, the uneven heating and cooling of thewall may weaken its structural integrity. A tilt-up wall with a fullyinsulated thermal mass is needed.

Therefore, it is an object of the invention to provide a process forcreating insulated tilt-up concrete panels. It is a further object thatthe tilt-up concrete panels be individually insulated on the exteriorsurface. It is another object of the invention to provide a process forcreating insulated tilt-up concrete panels which improves the efficiencyof on-site panel construction.

SUMMARY OF THE INVENTION

This invention is a method of making insulated concrete tilt-up panelsand the resultant products. An insulating material is formed into adesired shape. Preferably, the insulating material is pre-formed rigidpolystyrene. A standard panel typically has a substantially rectangularinsulating material, while custom panels may have irregular shapes, suchas cutouts for a door or window. Multiple panels of a given shape may bepre-made for use in a construction project where the panel shapes arerepeatedly used.

One or more attachment grooves are formed across the surface of theinsulating material. Preferably, the attachment grooves have asubstantially triangular cross-section. One edge of the insulatingmaterial may be formed with a tongue and the opposing edge formed with agroove, or the edges may be interlocking, such that one panel may beeasily and securely attached to another panel.

One or more segments of insulating material are laid horizontally withina conventional concrete tilt-up panel form. If multiple segments areused in a single form, each seam between the segments may be sealed toprevent seeping of wet concrete. The attachment grooves face up toreceive the concrete. The concrete is poured onto the insulatingmaterial until the form is filled. The concrete fills the triangulargrooves, thus attaching the insulation to the concrete panel. When theconcrete is cured, the panel may be stood up and set in place so thatthe insulating material forms the exterior surface of the panel.

A combination of four panels, each having a different shape, isdisclosed which may be used to build the exterior walls of multiplemodels of residential homes, such as those in a subdivision oflow-income housing. The insulating material may be prepared in thequantity desired for the entire construction project and transported toa casting area at the construction site. The panels may be rapidly castand assembled, reducing the time and labor required to complete theproject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of insulating material with the attachmentgrooves facing up.

FIGS. 2 a-2 f are cross-section views of various shapes of theattachment grooves.

FIG. 3 is a perspective view of an alternative embodiment of insulatingmaterial showing the attachment grooves in combination with attachmentperforations.

FIG. 4 a is a cross-section view of an attachment perforation.

FIG. 4 b is a top view of an attachment perforation.

FIGS. 5 a-d are perspective views of various edge shapes which may beused on the insulating material or its segments.

FIG. 6 is a perspective view of three segments of insulating materialconnected to each other and lying on a casting surface and within aconcrete form.

FIG. 7 is a perspective view of the segments of insulating material ofFIG. 6 connected to each other with glued seams.

FIG. 8 is a perspective view of three segments of insulating materialand spacing material within a concrete form.

FIG. 9 a is a partial end view of two segments of insulating materialconnected to each other with a glued seam.

FIG. 9 b is partial, isometric end view of an insulated tilt-up panel,in which the insulating material is resting atop the concrete.

FIG. 10 a is a perspective view of the casting surface, concrete form,and insulating material of FIG. 6 with rebar added to the concrete form.

FIG. 10 b is a cross section view of an insulated tilt-up panel,illustrating the rebar chair supporting the rebar.

FIGS. 11 a-f are cross-section views of various methods of sealing ajoint.

FIG. 12 is a front view of a panel set for building low-income homes.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1-12 illustrate a concrete tilt-up wall panel 10 in accordancewith the present invention. The exterior walls of a structure are formedby erecting and arranging a plurality of concrete tilt-up wall panels,referred to herein as panels 10, and permanently connecting the panels10 to each other. A panel 10 comprises concrete 11, which may be anybuilding concrete desired by the builder, and an insulating material 12.

Insulating Material

The insulating material 12 is preferably a substantially rigidinsulating foam which may be cut with a hot knife and will not bedamaged when wet concrete is poured onto it as explained below. Further,the insulating material 12 preferably has an R-value, used in the art tomeasure resistance to heat flow, of four per inch or higher. Twoexamples of such material which are known in the art are molded expandedpolystyrene (“MEPS”) and extruded expanded polystyrene (“EEPS”). In thepresent invention, EEPS is preferred due to its higher resistance towater vapor and heat flow. The insulating material 12 most preferablyhas an R-value of 4.5 per inch. Other polymer foams having a higherdensity and R-value, such as polyisocyanurate or polyurethane, may beused.

Some MEPS and EEPS insulating foam has a thin material, called facing,applied to its outer surfaces in order to protect the foam from damageduring handling. Some types of facing may also form a vapor barrier andincrease the insulating material's 12 resistance to heat flow. Thefacing may be a polymeric film, aluminum foil, kraft paper, or anotherthin protective layer. In the present invention, insulating foam havingfacing has been shown to perform better than foam without facing.Preferably, a facing is used that has increased vapor impermeability,such as a polymeric film.

To make a panel 10, the insulating material 12 is formed into a desiredshape and thickness. As used in the present disclosure, “shape” refersto the two-dimensional outline of a component. For example, theinsulating material 12 may have the shape of a rectangle and a thicknessof two inches or more. See FIG. 1. The insulating material 12 may beformed as a single piece for each panel 10, or it may be formed insegments 13 which are fit together in a panel 10, as shown in FIG. 6 anddescribed below.

One or more attachment grooves 14 are cut, such as by a hot knife, intothe insulating material 12. The attachment grooves are shaped so thatwhen concrete hardens in them the concrete is prevented from beingpulled out of the groove because the foam acts as a physical barrier toblock it. In other words, the maximum width of the portion of theattachment groove 14 that extends into the insulating material 12 iswider than the opening of the attachment groove 14 on the surface of theinsulating material 12. In the preferred embodiment, at least part ofthe attachment groove 14 has a substantially triangular cross-section,as shown in FIGS. 2 a-2 e. These figures are not exhaustive, and variousangles, base widths, sizes, and heights will suffice, depending on thematerial properties, cost, and manufacturing factors of the insulatingmaterials, cutting tool, and concrete. The triangle shape may also havea neck attached, as shown in FIG. 3 a. Alternatively, any groove shapethat prevents hardened concrete from being pulled out of the groove willsuffice, such as oval, spherical, elliptical, or trapezoidal shapes.Again, this list is not exhaustive, and various shapes, angles, widths,diameters, and heights will suffice, depending on factors such as thematerial properties, cost, and manufacturing factors of the insulatingmaterials, cutting tool, and concrete.

Preferably there are at least two attachment grooves 14 per segment 13of insulation material 12. The attachment grooves 14 may run parallel orperpendicular to the structure foundation, but preferably areperpendicular to it. In an alternative embodiment, attachmentperforations 15 are made in the foam panel. See FIGS. 3 and 4 a-b. Theseattachment perforations 15 may be used alone or in conjunction with theattachment grooves. In the alternative embodiment, the attachmentperforation 15 is a substantially cylindrical groove formed in theinsulation. The attachment perforations 15 may be formed by machinessimilar to lawn aerators, with pegs extending from a rolling cylinder.Preferably the attachment perforations do not extend entirely throughthe foam panel, but they may do so, depending on factors such asmaterial properties, cost, and manufacturing factors of the insulatingmaterials, cutting tool, and concrete.

The edges 16 of the insulating material 12, including the edges 16 ofany individual segments 13, are preferably squared off to provide asmooth contact surface when separate pieces of insulating material 12,or separate segments 13, are laid next to each other. See FIG. 5 a.Alternatively, the edges 16 may be fashioned into joint structures suchas a tongue and groove, mortise and tenon, or interlocking pattern. SeeFIGS. 5 b-c.

Casting

Referring to FIG. 6, a panel 10 is formed on a casting surface 30,preferably a substantially smooth concrete slab that is larger than thepanel 10, such as the pad of a foundation of a house, or a parking lot.The insulating material 12 is placed flat on the casting surface 30,grooved side up, within a concrete form 31 which will determine theshape of the panel 10. If the insulating material 12 is divided intosegments 13, the segments 13 are fit together within the concrete form31. The segments 13 are then attached together, and the seams 18 betweenthem sealed, by a sealant 17. See FIG. 7. The sealant 17 may be any typeof adhesive compound or other substance that will adhere to theinsulating material 12 and seal the seam 18, such as adhesive-backedpaper or plastic, duct tape, joint tape, caulk, joint compound, orexpanding foam glue, and preferably has insulating properties similar tothe insulating material 12. In the preferred embodiment, the sealant 17is a heat- and water-resistant expanding foam glue. Examples of such aglue are made by Hilti® and Touch ‘n’ Seal®.

In one embodiment, shown in FIG. 6, the shape of the insulating material12 is the same as the shape of the concrete form 31. This embodiment isuseful when casting a complete wall as a single panel 10. The jointsbetween walls can then be capped as described below. In anotherembodiment, shown in FIG. 8, the shape of the insulating material 12 issmaller than the shape of the concrete form, leaving space between theinsulating material 12 and the concrete form 31 on at least one side.This space may be filled by a spacing material 32 which is composed ofor coated with a material that will not bond to wet concrete.Preferably, the spacing material 32 has the same thickness as theinsulating material 12 and is sized to completely fill the empty space.The resulting panel 10 would have a solid concrete component 11 whichextends past the insulating material 12 on any side on which the spacingmaterial 32 was used during casting. As described below, and illustratedin FIGS. 11 b-c, this allows two such panels 10 to be erected andattached to each other from outside the structure, and the joint betweentwo such panels 10 to be covered by additional insulation when thepanels 10 are erected.

Once the insulating material 12 and any spacing material 32 is in placewithin the concrete form 31, wet concrete 11 is poured into the concreteform 31 on top of the insulating material 12. The wet concrete 11 fillsthe attachment grooves 14 and any attachment perforations 15. See FIG.9. Once the concrete form 31 contains the desired amount of concrete 11,the surface tension of the concrete 11 against the insulating material12 may cause the concrete 11 to adhere to the insulating material 12.Further, some of the wet concrete may seep into the interstitial spacewithin the insulating material 12. If this adhesion is not desired, itmay be prevented by using an insulating material 12 that has a facing asdescribed above. Another effect of the weight of the wet concrete 11 isthat it may press as much concrete 11 into the attachment groove 14 aspossible, partially compressing the insulating material 12 into thesides of the groove and more firmly attaching the concrete 11 to theinsulating material 12.

Referring to FIG. 10 a, one or more reinforcement structures 33 may beadded to the concrete form 31 to strengthen the panel 10. Thereinforcement structures 33 are positioned so they are at leastpartially encased by the concrete 11 when it is poured into the concreteform 31, and may extend out of the concrete 11 so that they may be usedto align the panel 10 or to attach other structures to the panel 10. Forexample, the reinforcement structures 33 may be metal ties, such asrebar, which span the panel 10 and will connect and maintain thepositions of additional panels 10 when the panels 10 are erected asdescribed below. A reinforcement structure 33 may also be a conventionalrebar chair for reinforcing the strength of the concrete panels, asshown in FIG. 10 b. Other examples of reinforcement structures 33 are aweld post, which protrudes from the concrete 11 near an edge; a threadedanchor bolt sleeve, which is encased in the concrete 11 except for atits mouth, which is open for receiving an anchor bolt; and a roofhanger, which may be partially or fully encased within the concrete 11and is positioned to receive a roof truss. Additional reinforcementstructures 33 are contemplated, which may be fully encased within theconcrete 11 or project outward from any surface of the panel 10. Oncethe desired amount of concrete 11 is poured into the concrete form 31,the interior surface 41 of the concrete 11 may be floated or otherwisefinished as desired. It is referred to as the interior surface 41because it will face into the structure when erected, so that wallstuds, drywall, or other interior building material may be attached toit.

When the concrete 11 cures, the panel 10 is finished. The interiorsurface 41 of the panel 10 is concrete 11 and the exterior surface 42,which faces away from the structure, is insulating material 12.

Erecting

Once cured, the panel 10 is tilted up, by means known in the art, andset in place in the structure. In one embodiment, the panel 10 is acomplete wall which is moved into place and then fastened to other wallsin the structure. In another embodiment, the panel 10 is part of acomplete wall which comprises more than one panel 10. In thisembodiment, each panel 10 is set in place and fastened to adjacentpanels 10.

A joint 50 is formed at each intersection of panels 10. The procedure offastening panels 10 together at each joint 50 may depend on how eachpanel 10 is cast. If a panel 10 is cast without a spacing material 32,the concrete 11 will be flush with the insulating material 12 at eachedge of the panel 10, as shown in FIG. 11 a. In this case, one or morefasteners 51 are attached to adjacent panels 10 on the interior surface41 of each panel 10, over the joint 50. A fastener 51 may be anyfastener capable of attaching tilt-up panels to each other and securingthem in place. Preferably, the fastener 51 is one or more welds, whereinweld posts 53 are inserted into the concrete 11 while it is curing, andwelding plates are attached to the weld posts 53 of adjacent panels 10.The seam 18 between the insulating material 12 of adjacent panels 10 maybe sealed by the sealant 17, applied from the exterior of the structure.

As shown in FIG. 11 b, when a panel 10 is cast using a spacing material32 on the panel 10 edges that are perpendicular to the structurefoundation, the joint 50 between two such panels will have spans ofconcrete 11 on either side which are not covered by insulating material12. One or more fasteners 51 may be attached on the structure's exteriorside, and an insulating insert 52, preferably composed of the samematerial as the insulating material 12, may be placed over the space toseal the joint 50, cover the uncovered concrete 11, and maintaincontinuity between the exterior surfaces 42 of the panels 10. Theinsulating insert 52 may be adhered to the concrete 11 using anadhesive, or it may be held in place by insulating filler 17 or anothersealant applied to the seams 18 between the insulating material 12 ofeach panel 10 and the insulating insert 52. As shown in FIGS. 11 c-e,the same procedure and materials may be used for capping corners formedby the intersection of two panels 10 and sealing the joint 50 created atthe intersection, as well as for covering connections to the roofing andfoundation of the structure. Due to increased exposure to water, thefasteners 51 used on the exterior of the structure should be stainlesssteel to avoid oxidation and weakening of the welds.

Once the panels 10 are secured in place, the exterior surface 42 of eachpanel 10 may be coated in a finishing material. The finishing material(not shown) may be any material which is used to create the desiredappearance of the structure from the outside, and which will not degradethe insulating material 12. Examples include house paint, stucco,shotcrete or other pneumatic concrete, and Gunite®. If an insulatingmaterial 12 having a facing was used, it may be necessary to remove thefacing on the exterior surface 42 in order to apply the finishingmaterial.

Example Panel Set—Low Income Housing

Referring to FIG. 12, a panel set of four panels 10 a-d includes all ofthe tilt-up wall panel shapes needed to build the exterior walls ofevery home in a subdivision of low-income housing. The panels 10 a-d areshown with triangular attachment grooves 14, but without anyreinforcement structures 33 so the shape of each panel 10 a-d is clearlyshown. For efficiency, the door and window heights and widths in eachhome are predetermined and uniform so that no panel shapes need to becustomized for individual homes. The panel shapes are: a standard panel10 a, which is preferably rectangular and is used for wall sections thatdo not require a door or window; a jamb panel 10 b, used where a door orwindow should be placed and having the same dimensions as the standardpanel 10 a, but having a substantially rectangular cutout at the top ofone side to receive the lintel, making the jamb panel 10 b substantiallyL-shaped; a lintel panel 10 c, which is preferably rectangular and formsthe top of a door jamb or window frame, fitting into the cutout in thejamb panel 10 b for support; and a sill panel 10 d, which is preferablyrectangular and forms the bottom of a window frame.

By limiting the panels 10 a-d to four shapes, the panels may be quicklymass-produced. Only four shapes of insulating material 12 and fourconcrete forms 31 are needed. The insulating material 12, concrete forms31, concrete 11, and other required building materials may betransported to and stored at the subdivision construction site. Labor isgreatly reduced during production of the panels 10 a-d because nocustomizing is necessary. Further, wall assembly workers will be able tofollow a uniform assembly process for each home. As a result,effectively insulated homes may be produced at a lower overall cost intime, labor and materials.

While there has been illustrated and described what is at presentconsidered to be the preferred embodiment of the present invention, itwill be understood by those skilled in the art that various changes andmodifications may be made and equivalents may be substituted forelements thereof without departing from the true scope of the invention.Therefore, it is intended that this invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

1. An insulated tilt-up wall panel comprising: a. an insulatingmaterial; b. one or more attachment grooves formed in the insulatingmaterial; and c. concrete attached to the insulating material by theattachment grooves.
 2. The insulated tilt-up wall panel of claim 1wherein the insulating material has substantially the same shape andperimeter as the concrete.
 3. The insulated tilt-up wall panel of claim1 wherein the insulating material has substantially the same shape asthe concrete and a shorter perimeter than the concrete.
 4. The insulatedtilt-up wall panel of claim 1 wherein the insulating material comprisesa plurality of adjacent segments.
 5. The insulated tilt-up wall panel ofclaim 4 wherein the insulating material further comprises an insulatingfiller, attached to the interior surface of the insulating material,which covers a seam between two adjacent segments.
 6. The insulatedtilt-up wall panel of claim 5 wherein the insulating filler is expandingfoam glue.
 7. The insulated tilt-up wall panel of claim 1wherein theinsulating material comprises an interior surface and an exteriorsurface and the attachment grooves are formed on the interior surface ofthe insulating material.
 8. The insulated tilt-up wall panel of claim 7wherein each attachment groove is narrower at the interior surface ofthe insulating material than the groove is inside the insulationmaterial.
 9. The insulated tilt-up wall panel of claim 8, wherein atleast a portion of the attachment groove has a substantially triangularcross section.
 10. The insulated tilt-up wall panel of claim 1 furthercomprising a reinforcement structure.
 11. The insulated tilt-up wallpanel of claim 10 wherein the reinforcement structure comprises rebar.12. A method of making an insulated tilt-up wall panel, the methodcomprising: a. forming an insulating material into a desired shape; b.forming one or more attachment grooves in the insulating material; c.placing the insulating material onto a substantially horizontal castingsurface and within a concrete form such that the opening of theattachment grooves faces up; and d. pouring a desired amount of concreteinto the concrete form, wherein the concrete substantially fills theattachment grooves and is attached to the insulating material when itcures.
 13. The method of claim 12 wherein the insulating materialcomprises a plurality of segments, and forming the insulating materialinto a desired shape comprises: a. arranging the segments into a desiredshape; and b. attaching each segment to one or more adjacent segments.14. The method of claim 12 further comprising positioning one or morereinforcement structures within the concrete form.
 15. A method ofbuilding a structure at a construction site using the tilt-up wall panelof claim 1, the method comprising: a. placing a plurality of tilt-upwall panels in a desired location such that the exterior surface of theinsulating material of each panel is substantially vertical, and eachpanel forms a joint with at least one other panel; b. at each joint,permanently attaching the tilt-up wall panels to each other; c. sealinga seam between the insulating material of adjacent panels; and d.applying a finishing material to the exterior surfaces of the insulatingmaterial of each panel.
 16. The method of claim 15 further comprisingcovering each joint with an insulating insert.
 17. The method of claim16 wherein permanently attaching the tilt-up wall panels forming thejoint to each other comprises welding one or more stainless steelfasteners to one or more stainless steel welding posts protruding fromthe concrete in each tilt-up wall panel.
 18. A set of insulated tilt-upwall panels for building a residential structure, the set comprising: a.a standard panel; b. a jamb panel; c. a lintel panel; and d. a sillpanel; wherein each panel comprises: i. an insulating material; ii. oneor more attachment grooves formed in the insulating material; and iii.concrete attached to the insulating material by the attachment grooves.19. The set of insulated tilt-up wall panels of claim 18 wherein thestandard panel, lintel panel, and sill panel are substantiallyrectangular and the jamb panel is substantially L-shaped.
 20. A methodof building a plurality of residential structures using the set ofinsulated tilt-up wall panels of claim 19, the method comprising: a.placing a plurality of each of the standard panels, the jamb panels, thelintel panels, and the sill panels in desired locations such that theinsulating material of each panel forms a substantially verticalexterior surface, and each panel forms a joint with at least one otherpanel; and b. at each joint, permanently attaching the panels to eachother.